Exhaust driven turbochargers include a rotating group that includes a turbine wheel and a compressor wheel that are connected to one another by a shaft. During operation, depending on factors such as sizes of various turbocharger components, a shaft may be expected to rotate at speeds in excess of 200,000 rpm. To ensure proper rotordynamic performance, a rotating group should be well balanced and well supported.
In many conventional arrangements, a turbocharger shaft is rotatably supported within a center housing by one or more bearings (e.g., oil lubricated, air bearings, ball bearings, magnetic bearings, etc.). In some arrangements, a bearing or bearings may be located in a bore of a center housing via one or more locating mechanism. For example, a locating pin may be employed as part of a locating mechanism to locate a semi-floating bearing in a bore of a housing where the locating pin is inserted into a locating pin bore of the housing accessible via a lubricant drain of the housing and pressed until it extends into the bore of the housing and into an opening in the semi-floating bearing. In such an arrangement, some clearance exists between an outer surface of the locating pin and an inner surface of the opening in the semi-floating bearing to allow the bearing to “float” on a lubricant film disposed between an outer surface of the bearing and an inner surface of the bore of the housing. Such a lubricant film may be referred to, for example, as a squeeze film damper (SFD), which may depend on geometry (e.g., length, diameter, radial clearance, etc.), lubricant characteristics (e.g., viscosity, temperature behavior, etc.), lubricant flow rate, lubricant pressure, etc.
In addition to lubricant dynamics, performance of a semi-floating bearing may be impacted by various mechanical factors. For example, as to clearance between an outer surface of a locating pin and an inner surface of an opening in a semi-floating bearing, mechanical factors such as surface roughness, wear, particulate generation, etc., may act to hinder beneficial movement of the bearing. In turn, such factors may reduce benefits provided by a squeeze film, for example, by altering geometry, pressure response, increasing friction force or other force associated with movement of a bearing with respect to a locating pin. Depending on the nature of hindrance to movement, a turbocharger may experience increased noise, vibration, harshness, wear, etc., and diminished performance and lifetime.
Technologies, techniques, etc., described in various examples herein can act to reduce risk of clearance-related issues associated with locating mechanisms for bearings. Such technologies, techniques, etc., may increase production quality, increase performance, reduce NVH, or achieve other benefits for turbomachinery.